EXCHANGE 


The  Effect  of  the  Age  of  Sire 

and  Dam  on  Offspring 

in  Dairy  Cows 


C.  L.  ALLEN 


Reprinted  without  change  of  paging,  from  the 
Journal  of  Heredity  (Organ  of  the  American 
Genetic  Association)',  Vol.  XIII,  No.  4;  Wash- 
ington, D.  C.,  April.  1922. 


THE  EFFECT  OF  THE  AGE  OF  SIRE 

AND  DAM  ON  THE  QUALITY  OF 

OFFSPRING  IN  DAIRY  COWS 


A  THESIS 


PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  IN  PARTIAL  FULFILLMENT 
OF  THE  REQUIREMENTS  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 

Ti.t 


BY 

CHARLES  LORING  ALLEN 

ii 


1920 


Reprinted  from  THE  JOURNAL  OF  HEREDITY  (Organ  of  the  American    Genetic 
Association),  Vol.  XIII,  No.  4  ;  Washington,  D.  C.,  April,  1922. 


ft' 


Sprinted,  without  change  of  paying,  front  the  Journal  of'lfrtetiity 
Genetic  Association),  Vol.  XIII,  No.  4;  Washington,  n.J 


^f  tiie  American 


THE  EFFECT  OF  THE  AGE  OF 

*  SIRE  AND   DAM  ON  THE 

*  QUALITY  OF  OFFSPRING 

IN  DAIRY  COWS 


C.  L.  ALLEX 

Cornell  University,  Ithaca,  N.  Y. 


A  FAMOUS  HOLSTEIN  SIRE 

FIGURE  10.  Ormsby  Korndyke  Lad  (102469)  one  of  the  great  sires  of  the  Holstein  Friesian 
Breed.  His  daughters  are  noted  for  their  high  production  records  for  both  7  day  and  yearly  work. 
He  has  18  daughters  with  records  of  over  30  pounds  of  butter  (80%  fat)  in  7  days.  He  also  has 
14  daughters  with  records  of  over  1000  pounds  of  butter  (80%  fat)  in  one  year.  The  sire  of  Ormsby 
Korndyke  Lad  was  only  23  months  of  age  when  he  was  born  and  his  dam  was  just  a  little  over  4 
years  of  age  (51  months).  Photograph  from  Holstein  Friesian  World. 


THE  effect  of  the  age  of  parents  on 
the  quality  of  the  offspring  is  in  a 
large  measure  concerned  with  the 
idea  of  cumulative  inheritance,  par- 
ticularly if  we  do  not  consider  the 
matter  of  the  proven  sire  or  dam. 
If  an  animal  is  a  more  valuable 
parent  after  it  has  attained  maturity, 
it  is  more  valuable  for  one  of  two  rea- 
sons. Either  the  mature  animal  must 
be  able,  merely  because  of  its  full 
physical  development  better  to  im- 


press its  characters  on  its  offspring,  or 
the  mature  animal  must  in  the  process 
of  attaining  maturity,  have  become 
endowed  with  something,  due  to  train- 
ing or  environment,  which  it  can  trans- 
mit to  its  progeny.  After  a  century  of 
study,  this  matter  is  far  from  settled 
and  the  question  as  to  the  possible 
effect  of  environment  on  the  transmis- 
sion of  a  tendency  to  increase  or  de- 
crease certain  quantitative  functions 
is  still  important. 


167 


'"the  Journal  of  Heredity 


JOHANNA  DE  KOL  CONCORDIA 

FIGURE  11.  At  three  and  a  half  years  of  age  her  record  was  19037  pounds  of  milk  and  671 
pounds  of  butterfat.  Her  sire,  Sir  Clothilde  Concordia,  was  two  years  nine  months  of  age  when 
she  was  born,  while  her  dam,  Cold  Spring  Johanna  De  Kol  2nd,  was  three  years  and  a  half  old. 
The  great  number  of  cases  where  the  parents  of  high  producing  cows  are  as  young,  or  younger 
than  these,  leaves  no  doubt  that  the  off-spring  of  immature  parents  are  just  as  good  producers  or 
transmitters  of  production  as  those  born  when  the  same  parents  are  mature.  Photo  by  U.  S. 
Department  of  Agriculture.  (See  text,  p.  173.) 

In  practical  breeding,  it  would  be 
very  advantageous  to  know  definitely 
whether  the  young  born  of  immature 
parents  are  as  valuable  for  production, 
and  for  reproducing  their  kind,  as 
those  born  of  more  mature  parents. 
It  is  the  aim  of  this  paper  to  show 
whether  the  parentage  of  a  group  of 
high  producing  or  superior  cows  aver- 
ages older  than  the  parentage  of  a  group 
of  comparatively  low  producing  or 
inferior  cows.  The  paper  also  attempts 
to  show  the  percentage  distribution  of 
offspring  for  the  various  ages  of  both 
sire  and  dam;  the  age  when  cows 
actually  make  their  best  records;  and 
whether  the  offspring  of  very  young  or 
very  old  animals  are  inferior. 


METHOD 

The  data  reported  in  this  paper  were 
taken  from  Volume  27  of  the  Ad- 
vanced Registry  Year  book  and  the 
Herd  Books  of  the  Holstein  Friesian 
Association  of  America. 

The  superior  class  of  animals  chosen 
include  those  that  up  to  April  30th, 
1916,  had  made  records  of  24  pounds 
or  more  of  butterfat  in  seven  days. 
This  included  all  of  the  so-called 
thirty  pound  cows  since  24  pounds  of 
butterfat  is  equal  to  30  pounds  of 
eighty  percent  butter.  For  purposes 
of  more  careful  study,  this  class  was 
divided  into  three  groups  as  follows: 

Group  I — All  cows  producing  over 
27.3  pounds  of  butterfat  in  7  days. 


Allen:  Effect  of  Parents'  Age  on  Quality  of  Dairy  Cows      169 


Group  II — All  cows  producing  be- 
tween 25.6  and  27. 3  pounds  of  butter- 
fat  in  7  days. 

Group  III — All  cows  producing  be- 
tween 24 . 0  and  25 . 6  pounds  of  butter- 
fat  in  7  days. 

The  comparatively  inferior  class  of 
animals  chosen  includes  all  of  the  so- 
called  mature  cows,  that  is,  cows  five 
years  of  age  or  over,  that  produced 
less  than  fourteen  pounds  of  butter- 
fat  in  seven  days  and  were  entered  in 
the  27th  Volume  of  the  Holstein  Frie- 
sian  Advanced  Registry  Year  Book  as 
entries  or  re-entries.  This  class  was 
divided  into  three  groups  that  were 
fairly  comparable  in  numbers  to  the 
groups  of  the  superior  class,  as  follows : 

Group  I — All  cows  producing  be- 
tween 12  and  12.5  pounds  of  butter- 
fat  in  7  days. 

Group  II — All  cows  producing 
between  12.5  and  13.0  pounds  of 
butterfat  in  7  days. 

Group  III — All  cows  producing  be- 
tween 13.0  and  14 . 0  pounds  of  butter- 
fat  in  7  days. 

The  groups  were  arranged  so  that 
the  very  highest  producers  were  in 
group  1  of  the  Superior  Class  and 
the  very  lowest  producers  were  in 
group  1  of  the  Inferior  Class.  Then, 
if  there  was  any  difference  in  age, 
it  was  thought  that  the  first  groups 
should  be  further  apart  than  the  second 
and  third  groups. 

The  7  day  record  was  chosen  as  the 
basis  for  this  study  because  a  larger 


number  of  records  were  available  and 
the  7  day  record  is  generally  recog- 
nized as  a  valuable  method  of  deter- 
mining the  productive  ability  of  dairy 
cows. 

Three  generation  pedigrees  were 
compiled  for  all  the  cows  of  both  the 
Superior  and  Inferior  Classes.  These 
pedigrees  included  the  date  of  birth 
for  all  animals  in  every  pedigree.  This 
makes  it  possible  to  compute  the  dif- 
ference in  age  between  any  animal  and 
its  parents  and  tells  us  the  age  of  the 
parents  at  the  time  the  animal  in 
question  was  born.  This  also  provides 
data  for  determining  the  average  differ- 
ence in  age  between  generations,  and 
allows  the  calculation  of  the  percentage 
distribution  of  offspring  according  to 
the  age  of  parents,  making  it  possible 
to  observe  whether  more  good  cows 
or  poor  cows  are  born  from  very  young 
or  very  old  dams.  The  difference  in 
age  between  parent  and  offspring  was 
computed  in  months  to  the  nearest 
month. 

In  order  to  determine  at  what  age 
the  superior  cows  made  their  records, 
it  was  necessary  to  take  this  data 
directly  from  the  Advanced  Registry 
Year  book  and  record  it  on  the  pedi- 
gree. 

RESULTS THE  DIFFERENCE  IN  AGE 

COMPARED 

Table  I  gives  the  average  age  of  the 
ancestry  of  the  Superior  and  the  Infer- 
ior Classes  by  groups  and  for  the  classes 


TABLE  I.  Average  Age,  in  Months,  of  Ancestry  of  Superior  and  of  Inferior  Classes  of  Cows 


Superior  Cows 

Inferior  Cows 

Ancestor 

Group  1 

Group  2 

Group  3 

Class 

Group  1 

Group  2 

Group  3 

Class 

Sire 

44.3 
62.8 
48.6 
64.9 
42.3 
65.2 
44.3 
61.3 

51.7 
63.6 
49.6 
65.2 
41.4 
63.0 
44.8 
59.0 

46.3 
61.2 
49.6 
67.6 
42.3 
59.6 
48.1 
63.8 

47  .  1  +  .  647 
61.  9  +  .  890 
49.5  +  .  717 
66.7  +  .  929 
42.1  +  .507 
61.0+.873 
46.9+.  640 
62.  5  +.939 

45.7 
60.0 
45.4 
66.5 
44.8 
65.0 
45.4 
61.7 

44.6 
62.2 
46.4 
69.4 
43.0 
69.4 
47.9 
72.1 

41.6 
64.7 
46.7 
65.8 
43.4 
62.8 
43.8 
64.7 

43.1+    .529 
63.1+    .941 
46.6+    .646 
66.7  +  1.034 
43.6+    .508 
64.7  +  1.013 
45.1+    .602 
65.7  +  1.006 

Dam  

Paternal  grand  sire  . 
Paternal  grand  dam. 
Maternal  grand  sire. 
Maternal  grand  dam 
Great  grand  sire1  .  .  . 
Great  grand  dam1  .  . 

Number  of  pedigrees 
in  each  group  and 
class  

86 

121 

404 

Jr~* 

611 

111 

114 

285 

510 

1  Great  grand  sire  refers  to  sire  of  paternal  grand  sire.    Great  grand  dam  refers  to  the  dam  of 
the  maternal  grand  dam. 


170 


The  Journal  of  Heredity 


as  a  whole.  This  table  allows  us  to 
make  comparisons  and  determine  any 
significant  difference  between  the  aver- 
age age  of  the  superior  cows  and  the 
(comparatively)  inferior  cows, 
i  It  will  be  noted  in  table  I  that 
the  greatest  difference  in  age  is  four 
months  and  that  this  occurs  in  the 
case  of  the  sires.  This  difference 
might  seem  to  be  somewhat  significant 
in  the  light  of  the  probable  error  as  a 
measure  of  its  probable  significance. 
The  difference  is  more  than  three 
times  the  probable  error  but  the  prob- 
able error  in  this  case  is  small.  We 
must  remember,  however,  that  four 
months  is  not  a  very  marked  difference 
and  this  difference  loses  a  large  part  of 
its  significance  when  we  study  the 
group  averages.  There  is  more  differ- 
ence between  the  groups  within  the 
classes  even  here  than  there  is  between 
the  classes  themselves.  This  is  still 
more  noticeable  in  other  places  in  the 
table  where  the  class  difference  is  not 
so  great.  Take  for  example,  the  case 
of  the  dams,  the  great  granddams,  or 
the  maternal  grand  sire.  In  each  of 
these  cases,  the  difference  is  probably 
insignificant  in  the  light  of  the  prob- 
able error,  and  in  each  case,  the  differ- 
ence between  the  groups  within  the 
class  is  greater  than  the  difference 
between  the  classes. 

The  real  difference  in  age  between 
the  various  parents  and  generations  is 
more  clearly  shown  by  means  of  a 
pedigree.  Such  a  pedigree  is  given  in 
Figure  12. 

It  is  evident  that  there  can  be  no 
increased  hereditary  value  due  to  the 
age  of  the  dams,  for  in  every  case  ex- 
cept one,  the  dams  of  the  Inferior  Class 
average  older,  though  not  significantly 
so,  than  the  dams  of  the  Superior  Class. 
In  the  one  case,  that  of  the  paternal 
granddam,  they  average  exactly  alike. 

From  a  study  of  Table  I  and  the 
pedigree,  Figure  12,  it  is  apparent 
that  there  is  no  significant  difference 
between  the  ages  of  parents  of  the 
Inferior  and  of  the  Superior  Classes. 
In  only  one  case  is  the  difference  out- 
side the  limits  defined  by  three  times 
the  probable  error.  In  this  case,  the 


small  difference  between  the  class 
averages  can  hardly  be  considered  sig- 
nificant when  there  is  so  great  a  differ- 
ence between  the  group  averages  within 
the  class. 

BULLS  ARE  NO  MORE  VALUABLE 
PARENTS  AS  THEY  GROW  OLD 

Turning  our  attention  again  to  the 
pedigree,  Figure  12,  we  note  that  in 
every  case  the  Superior  sires  on  the  top 
line  of  the  pedigree  are  older  than  the 
corresponding  inferior  sires.  The  dif- 
ference is  probably  not  significant 
even  in  the  case  of  the  sires,  but  the 
tendency  persists. 

This  led  to  a  study  to  determine 
whether  a  bull  produced  superior 
offspring  as  he  grew  older.  From  a 
study  of  four  bulls  having  a  total  of 
five  hundred  and  six  daughters,  it 
seems  that  bulls  may  or  may  not  have 
better  daughters  as  they  grow  older, 
depending  on  the  quality  of  animals  to 
which  they  are  bred.  As  a  bull  proves 
his  superior  worth,  he  is  very  likely  to 
be  bred  to  better  cows  and  produce 
better  offspring.  This  probably  ac- 
counts for  the  difference  shown  in  the 
pedigree.  This  whole  matter  will  be 
fully  discussed  in  a  later  paper.  Thus 
the  difference  in  age  of  sires  can  be 
very  readily  assigned  to  the  use  of  the 
sires  and  there  is  no  indication  that 
the  sires  are  any  better  when  they  are 
old  than  when  young  and  immature. 
In  fact  the  frequency  distribution, 
Figures  13  and  14,  tends  to  show  that 
the  young  parent  of  either  sex  is  just  as 
valuable  as  a  parent  when  immature 
as  it  is  in  later  life.  The  frequency 
curves  include  only  the  sires  and  dams 
of  the  first  generation. 

FREQUENCY  DISTRIBUTION  ACCORD- 
ING TO  AGE  OF  SIRE 

In  the  frequency  curves,  Figures 
13  and  14,  it  will  be  observed  that 
the  curves  run  very  nearly  parallel 
throughout.  The  curves  start  high, 
indicating  that  a  large  percentage 
of  cows  in  both  the  Superior  and 
Inferior  Classes  are  sired  by  very 
young  bulls.  In  this  connection,  it 
will  be  remembered  from  Table  I  that 


Allen:  Effect  of  Parents'  Age  on  Quality  of  Dairy  Cows      171 


46.9 

45.1 

Great  Grand  Sire 


49.5 

46.6 

Grand  Sire 


47.1 

43.1 


Sire 


Grand  Dam. 
66.7 

66.7 


42.1 

43.6 

Grand  Sire 


Dam 


61.9 
63,1 

Grand  Dam 
61.0 

64.7 

Great  Grand  Dam 
62  5 
65.7 

AN  AGE-PEDIGREE  OF  THE  TWO  CLASSES  OF  COWS 

FIGURE  12.  This  shows  the  average  age  of  the  ancestors  of  the  superior  cows  (Bold-face  type), 
and  of  the  inferior  cows  (Italics).  It  is  evident  that  there  are  no  significant  differences  in  the  age 
)f  the  forebears  of  the  two  classes.  (See  text,  p.  169.) 


he  sires  of  the  Superior  Class  average 
ess  than  four  years  of  age,  46 . 4  months 
;o  be  exact,  and  that  the  sires  of  the 
inferior  Class  average  somewhat 
younger.  The  largest  number  of  off- 
spring were  born  when  their  sires  were 
rom  two  and  one-half  to  three  years 
)f  age.  This  means  that  these  bulls 
sired  a  larger  percentage  of  their  off- 
spring between  twenty-two  and  twenty- 
seven  months  of  age  than  at  any 
ther  time. 

Table  II  shows  very  clearly  just 
how  our  purebred  sires  are  used.  It 
ndicates  that  improvement  has  been 
based  on  the  selection  of  young  sires 
rather  than  on  the  use  of  tried  sires. 

THE  PROVEN  SIRE 

A  bull  cannot  be  called  a  proven  sire 
until  his  first  crop  of  heifers  come  in 
milk  and  can  hardly  be  so  called 
until  these  heifers  have  milked  at 
east  one  year.  Thus  a  bull  can  hardly 


be  called  a  proven  sire  until  he  is  five 
years  of  age.  In  general  practice,  the 
percentage  of  cows  sired  by  unproven 
bulls  is  probably  much  higher  than  the 
percentage  shown  for  the  animals  in- 
cluded in  this  study.  This  means  that 
even  the  breeders  who  are  making 
records  use  a  tried  sire  for  only  a 
small  percentage  of  their  cows.  That 
the  tried  sire  is  more  valuable  is  indi- 
cated by  the  fact  that  21.1  percent  of 
the  Superior  cows  are  daughters  of 
tried  sires,  whereas  only  15.9  percent 
of  the  Inferior  cows  are  daughters  of 
bulls  of  an  equal  age.  This  may  seem 
to  conflict  with  the  idea  that  the  bull 
when  old  is  not  more  valuable,  but 
the  paper  referred  to  above  shows  that 
he  is  not  more  valuable  as  a  parent. 

FREQUENCY  DISTRIBUTION  ACCORD- 
ING TO  AGE  OF  DAM 

The  frequency  curve  for  the  dams, 
Figure  13,  is  very  much  more  irregular 
than  the  curve  for  the  sires  but  on  the 


172 


The  Journal  of  Heredity 


rr 

SUPERIOR   CLASS 
INFERIOR  CLAS 

i 

-» 

1 

x' 

1     / 

I 

3s 

1 

Y      > 

^  —  ' 

J 

| 

\ 

; 

f 

/. 
\f 

\ 

I 

\ 

I 

\ 

\ 

\\ 

'  1 

\ 

j 

1 

1 

\ 

/ 

\ 

\ 

/ 

\ 

\l 

3 

H 

i\\j  ^ 

1  \  r/ 

\ 

\\\ 

5 

V 

fv 

1 

... 

\ 

V 

__. 

5 

•  — 

x 

-<- 

4    30    36     42    48    54    60     66    72    78     84     90     96    102 

108    114    '20    126   132    138  144   150    156   1G2    168   174    180   186 

192    198  2 

AGE  OF  DAMS  IN  MONTHS 
FREQUENCY  CURVE  FOR  DAMS 

FIGURE  13.  The  percentage  of  young  born  by  dams  of  various  ages  is  shown  in  this  chart. 
The  age  of  the  dams  is  computed  for  six-months  periods,  and  the  upper  age  limit  of  these  groups 
is  shown.  That  is,  all  the  dams  24  months  and  under  are  considered  24  months  old,  those  between 
24  and  thirty  months  of  age,  as  30  months  old,  etc.  It  is  evident  that  much  the  greater  number 
of  calves  are  born  by  very  young  cows,  the  quality  of  whose  offspring  cannot  be  known.  (See  text, 
p.  171.) 


Allen:  Effect  of  Parents'  Age  on  Quality  of  Dairy  Cows      173 


whole,  even  here,  the 
curves  run  nearly 
parallel.  There  is, 
however,  a  distinctly 
larger  percentage  of 
high  producers  born 
of  very  young  dams 
than  there  is  of  low 
prod ucers.  1 1  is  hard 
to  account  for  this 
unless  the  Superior 
Class  have  received 
better  care  and  are 
bred  younger  on  the 
average  than  the  In- 
ferior Class. 

It  will  be  noted  in 
connection  with  Table 
III  that  a  slightly 
larger  percentage  of 
the  Superior  Class 
were  born  from  dams 
under  five  years  of 
age  than  there  were 
of  the  Inferior  Class. 
In  later  life,  the  two 
classes  are  very  near- 
ly alike  and  almost 
exactly  as  many  of 
the  Superior  Class 
were  born  from  dams 
over  eight  years  of 
age  as  were  born  in 
the  Inferior  Class 
from  dams  of  a 
like  age.  The  per- 
centage having  dams 
over  twelve  years  is 
exactly  alike  for  both 
classes. 

VALUE  OF  OFFSPRING 

OF  VERY  YOUNG 

AND  VERY  OLD 

PARENTS 

From  a  study  of 
the  frequency  curves 
and  Tables  II  and 
III,  it  is  evident  that 
the  young  born  from 
very  young  parents  or 
from  very  old  parents 
are  as  valuable  as 
any  for  productive 


18. Or 
17.5 


17.0 


15.5 


15.0 


I4.0t 

I3.5F 


13.0 


SUPERIOR  CLASS 
INFERIOR  CLASS 


y\ 


24  30    36   42    48    54    60   66    72    78    84    90   96    102  108   114   120  126   132  138  144 

AGE  OF  ^SH  IN  MONTHS 
FREQUENCY  CURVE  FOR  SIRES 

FIGURE  14.  The  co-ordinates  are  the  same  as  in  the  preceding 
chart.  The  same  conclusions  apply  even  more  strikingly  in  this 
case,  as  the  sires  are  not  used  for  breeding  purposes  as  long  as  the 
dams.  A  sire  cannot  be  considered  a  proven  sire  until  his  first 
crop  of  daughters  have  been  in  milk  at  least  a  year,  which  means 
that  he  must  be  five  years  of  age.  These  figures  are  for  a  selected 
class  of  sires  and  show  that  even  the  breeders  who  are  making 
records  use  tried  sires  for  only  a  small  percentage  of  their  cows. 
(See  text,  p.  170.) 


The  Journal  of  Heredity 


WATSON  SEGIS  PONTIAC  HOMESTEAD 

FIGURE  15.  She  was  born  when  her  dam,  Watson  Segis  Pontiac,  was  just  2  years,  2  days  old, 
when  her  sire,  Piebe  Laura  Allie  Homestead  King,  was  a  senior  two-year-old.  Her  record  is 
25,360  pounds  of  milk  and  928  pounds  of  fat.  Her  mother  has  a  record  of  844  pounds  of  fat,  and 
she  is  the  daughter  of  King  Segis  Pontiac  Count,  a  great  breeding  sire,  who  was  only  a  little  over 
two  years  old  when  she  was  born.  Photo  by  U.  S.  Department  of  Agriculture. 


TABLE  II.     The  Percentage  of  Daughters  Born  on  or  before  a  Given  Age  of  Sire,  and  the  Age 
of  the  Sire  at  "the  Time  the  Dams  of  the  Daughters  were  Bred 


Age  of  Sire  when  Daughters 
were  born 

Age  of  Sire  when  the  Dams  of 
Daughters  were  Bred 

Percentage  of  Daughters 

Superior 

Inferior 

30  Months  and  Under 
36  Months  and  Under 
60  Months  and  Under 
Over  60  Months 

21  Months  and  Under 
27  Months  and  Under 
51  Months  and  Under 
Over  51  Months 

27.5 
45.3 
78.9 
21.1 

28.0 
45.3 
84.1      - 
15.9 

TABLE  III.    Showing  the  Percentage  of  Young  Born  Before  and  After  a  Given  Age  of  Dam 


Age  of  Dam  when  Daughters 
were  born 

Percentage  of  Superior 
Daughters 

Percentage  of  Inferior 
Daughters 

30  Months  and  Under 

17  2 

13  3 

36  Months  and  Under 

26  2 

21  6 

60  Months  and  Under  

57   1 

54  9 

Over  8  years 

14  8 

15  0 

Over  12  Years  

y* 

.      2.8 

Allen:  Effect  of  Parents'  Age  on  Quality  of  Dairy  Cows      175 


A  SIRE  OF  RECORD-MAKING  DAUGHTERS 

FIGURE  16.  King  Hengeveld  Aaggie  Fayne  (56635)  has  shown  remarkable  ability  to  transmit 
production.  He  was  slaughtered  when  only  three  years  of  age  and  as  a  result  has  only  31  A.  R.  O. 
daughters.  Eleven  of  these  daughters  have  records  in  excess  of  30  pounds  of  butter  (80%  fat) 
in  7  days.  Four  of  his  daughters  have  yearly  records.  Three  of  these  records  made  by  two  and 
three  year  old  heifers  average  2 1,762 . 2  pounds  of  milk  and  978 . 93  pounds  of  butterfat.  The  other 
yearly  record  was  made  by  a  mature  daughter  and  is  15,486.1  pounds  of  milk  and  530.89  pounds 
of  butterfat. 

King  Hengeveld  Aaggie  Fayne  was  born  when  his  parents  were  quite  young.  His  sire  was 
22  months  of  age  and  his  dam  28  months  of  age  when  he  was  born.  Photo  by  the  Holstein-Fresian 
World. 


purposes.  An  unusually  large  percent- 
age of  the  Superior  Class  were  born 
before  their  dams  were  two  and  one- 
half  years  of  age  and  must  have  been 
first  calves.  The  sires  of  a  large  per- 
centage of  the  Superior  Class  were  also 
under  two  and  one-half  years  when  the 
dams  were  bred.  On  the  other  hand, 
just  as  large  a  percentage  of  the 
Superior  Class  as  of  the  Inferior  Class 
is  from  very  old  parents. 


AGE  WHEN  THE  BEST  RECORDS  ARE 
MADE 

Table  IV  was  arranged  for  the  Supe- 
rior Class  only.  The  best  record  was 
used  in  every  case.  If  any  of  the  cows 
herein  considered  have  made  a  better 
record  since  the  collection  of  this 
data  this  fact  introduces  an  error. 
It  is  recognized  that  only  a  very  few 
cows  have  ever  made  more  than  one 


TABLE  IV.   The  Average  Age  of  All  the  Superior  Cows  at  the  Time  Their 
Records  Were  Made 


Group  I 

Group  II 

Group  III 

Superior  Class 

Number  of  Cows 

86 

121 

404 

611 

Average  Age  in  Months.  . 

69.7 

72.1 

73.7 

72.2 

1 76 


The  Journal  of  Heredity 


record  above  thirty  pounds  of  butter 
in  a  week  and  most  of  those  that 
have  done  so  are  here  considered.  This 
error,  then,  is  in  all  probability  very 
small. 

The  group  averages  and  the  class 
average  all  show  that  the  best  records 
of  the  animals  herein  considered  were 
made  at  an  average  age  of  about  six 
years.  Of  course  many  were  much 
older  than  this  and  many  were  younger, 
but  it  is  well  known  that  animals  vary 
greatly  in  rapidity  of  development. 
It  would  seem  that  the  numbers  con- 
sidered are  large  enough  to  make  the 
average  significant  even  though  it  is 
recognized  that  most  cows  do  not  have 
a  chance  to  make  a  record  every  year. 
The  cow  is  most  likely  to  be  tested  at 
the  time  she  shows  greatest  promise. 
Since  these  high  producers  made  their 
best  records  at  six  years  of  age,  it 
seems  only  fair  to  assume  that  they 
were  at  the  height  of  their  productive 
capacity  at  this  time.  It  would  also 
indicate  that  cows  generally  reach  the 


limit  of  their  possibilities  for  high 
production  at  about  this  age.  This 
contention  is  supported  from  other 
sources,1  although  one  investigator,2 
who  attacked  the  problem  in  an 
entirely  different  manner,  maintains 
that  the  highest  production  is  not 
reached  until  much  later  in  life. 

SUMMARY 

The  parentage  of  superior  or  high 
producing  dairy  cows  is  no  older  than 
the  parentage  of  comparatively  inferior 
or  low  producing  cows  and  thus  the  old 
animal  is  no  more  valuable  as  a  parent 
than  the  young  animal. 

As  far  as  the  age  of  either  parent  is 
concerned,  the  young  born  at  one  time 
in  life  seem  to  be  just  as  valuable  as 
the  young  born  at  any  other  time. 

A  very  large  percentage  of  our  cows 
are  born  of  immature  parents  but  the 
proven  animal  at  any  age  is  much  more 
valuable  for  breeding  purposes. 

On  the  average,  cows  make  their 
best  records  at  about  six  years  of  age. 


1  PEARL  RAYMOND,  The  Change  of  Milk  Flow  with  Age. 
Station  Bulletin,  No.  262.     1917. 

2  GOWAN,  J.  W.,  Studies  in  Milk  Secretion  VIII. 
Bulletin,  No.  293.     1920. 


Maine  Agricultural  Experiment 


Maine  Agricultural  Expiriment  Station 


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UNIVERSITY  OF  CALIFORNIA  LIBRARY 


